Apparatus for measuring or indicating movement by combined encoding and counting

ABSTRACT

Relative movement between two members is sensed by a device yielding a signal during successive increments of movement. A first circuit means applies one pulse to a reversible counter for each incremental movement and a second circuit controls the direction of counting to accord with that of movement.

UHBiiQ Taisne 235/92 V, 92 GD DISCRIMINATING NETWORK TOGGLE FORMlNGCIRCUIT FLIP FLOP TIME DELAY CIRCUIT 1 1 Apr. 24, 1973 l l APPARATUS FORMEASURING OR [56] References Cited INDICATING MOVEMENT BY E P NTSCOMBINED ENCODING AND UNITED STAT S ATE COUNTING 3.562,498 2/1971Darling ..235/92 EV I 3,142,121 7/1964 Stefanov ....235/92 GC [75 lInventor Jean 3,337,723 8/1967 Etnyre .235 92 EV France [73] Assignee:Societe DOptique, Precision Elec- Primary Examiner-Maynard R. Wilburtronique Et Mecanique-Sopelem, Assistant ExaminerRobert F. Gnuse Paris.France Attorney-Cameron, Kerkam & Sutton 22 F'led: ul 8,1971 l l J y 57ABSTRACT [21] Appl. No.: 160,731

Relative movement between two members is sensed [31)] ForeignApplieuiion lri (Trity Data by a device yielding a signal duringsuccessive increments of movement. A first circuit means applies oneJuly 30,1970 France ..7()28153 pulse to a reversible counter for eachincremental 52 us 1 235 92 235 92 R, 235 92 v movement and a secondcircuit controls the direction 235/92 LG, 340/347 p of counting toaccord with that of movement. [51] Int. Cl. ..H03k 21/04 [58] Field ofSearch .235/92 EV, 92 LG, 9 3 Dmw'ng F'gures COUNTING PULSE GENERATINGROUTING Patented April 24, 1 973 I v 3,729,621

5 Sheets-$11 8 1 Q a I 1 1 3 cons l CONVERTER-" Fl commas I c iirms olscgw g m cmcun' L11 1 -TOGGLE TIME DELAY 151 I CIRCUIT 5 I I 42 Q aSTORAGE FLIP FLOP T 1 ROUTlNG 1 \-SIGNAL 8 cmcun GENERATING 14 CIRCUIT rl I Q O 0 0 PULSE FORMING M l t r :JTF\\9 CIRCUIT n REVERSIBLE COUNTERPatented April 24, 1973 3,729,621

3 Shoots-Sheet 2 FIG-.2

CODE CONVERTER 4 couNTms l PULSE GENERATING 6 cmcun 3. 3. J 3 -1 3 j x 112 'mEC T i i ROUTING I cmcuag/T "1 RECORDING RCUIT J PULSE FORMINGClRCUlT REVERSIBLE COUNTER APPARATUS FOR MEASURING OR TNDICATHNGMOVEMENT BY COMBINED ENCODING AND COUNTING This invention relates toapparatus for measuring or indicating movement by combined encoding andcounting, more particularly for indicating the position of one movingpart relative to another in numerically controlled machines.

Systems of this type, of course, can use either absolute digitalmeasuring methods, in which the position of the moving part is indicatedrelative to an encoded scale giving a coded indication of each positionof a scanning device, or pulse counting methods, which also use ascanning device moving across a graduated scale, but in which the pulsesdeveloped by the scanning device as it passes across the graduations ofthe scale are counted, the total indicated by the counter representingthe position for the moving part. To avoid restricting the length of theincrement, that is to say, the movement unit which the scanning devicecan indicate, it has been proposed that both systems should be combinedto give combined encoding and counting methods. In such combinedsystems, the scanning device is composed of a plurality of offsetsensors moving across the graduations of the scale and transmittingtrains of phase-shifted repetitive signals,-

these signals being first shaped by comparison with a reference signaland then combined in a code conversion network having n output gates,each of which transmits a network signal, each of these network signalsC C C comprising in turn, during a movement equal to the pitch of thescale, a square-wave pulse whose width corresponds to one unit ofmovement.

The square-wave pulses thus provided by one output gate of the codeconversion network for every movement of one increment are convertedinto counting pulses which are summed in a reversible counter. Thepulses may be shaped in any known manner in a pulse generating networkwhich, for example by means of a differentiating circuit, will make onecounting pulse correspond to each rising slope in the square-wave pulseexhibited by one of the network signals C C C C However, a network fordiscriminating the direction of movement of the scanning device is alsorequired, so that the pulses are counted, that is, added to the totalindicated by the counter, when the scanning device moves across thescale in a direction selected as the positive direction, and arededucted, that is, subtracted from the total indicated by the counter,when the scanning device moves in the opposite or negative, direction.

In general, the direction of movement discriminating network comprises atime-delay circuit for each signal C each delayed signal being thencompared with the adjacent signals C and C an AND gate. When thescanning device is moved in the positive direction, the signal Cexhibits a square-wave pulse and the conjunction of this pulse and ofthe delayed pulse of the signal C supplies a square-wave pulse whosewidth corresponds to the delay of the signal C Similarly, when thescanning device moves in the negative direction, the conjunction of thesignals C and C produces a square-wave pulse of brief duration.Generally it is the pulses so formed which are fed to set whereas thepulses must be deducted if the scanning device is moving in the negativedirection, they must be counted again if the counter passes through zerowhile the scanning device is still moving in the negative direction. Forthis reason it is necessary to provide a network for determining thecounting direction, so that the position of the zero can be taken intoaccount.

According to the present invention, there is provided apparatus formeasuring or indicating movement by encoding and counting, comprising agraduated scale, a travel measuring device having n output gates eachproviding a unique signal, these unique signals exhibiting in successionduring movementequal to one scale pitch a square-wave pulse of which thewidth corresponds to one increment of movement, a first circuit meansfor generating one counting pulse for each increment of movement, asecond circuit means for determining the direction of counting, and areversible counter having one input for pulses to be added and anotherinput for pulses to be subtracted and supplying an algebraic valuerepresenting the position relative to an origin, of the travel measuringdevice, said first and second circuit means being connected in parallelbetween the ri output gates of the travel measuring device and a routingcircuit which has two outputs connected respectively to the adding andto the subtracting inputs of the reversible counter and which receiveson one input the counting pulses produced by the first circuit means andon another input a signal, produced by said second circuit means,controlling the routing of the counting pulses to one input or the otherof the counter.

In one embodiment said second circuit means comprises a network fordiscriminating the direction of movement, a toggle for storing thedirection of movement, a manually preset master-slave toggle for storingthe sign of the position reading, a circuit operated by the outputsignals of the toggles for generating a signal controlling the directionof counting, a test circuit for detecting a change to zero of thecounter state, the output of the circuit for controlling the directionof counting and that of the test circuit being connected to the inputsof a gate of which the output signal is applied both to cause thesign-storing toggle to change its state and to the input of a circuitcapable of forming two phase-shifted supplementary pulses which arearranged to be applied to the input for the counting pulses of saidrouting circuit.

The system embodying the invention permits a general simplification ofthe installations normally used while differentiating between thenetwork for shaping the pulses and the network for determining thecounting direction.

The invention will now be described in more detail with reference to aparticular embodiment, given by way of example and illustrated in theaccompanying drawings, in which:

FIG. 1 is a general diagram of a movement measuring system embodying theinvention;

FIG. 2 is a diagram representing a preferred embodiment of theinvention; and

FIG. 3 is a detail showing the circuit means for determining thecounting direction.

FIG. 1 shows part only of a graduated scale 1 provided on one part ofthe machine, the travel measuring device being on another part movablerelative to the first part. The travel measuring device includes ascanning device comprising a plurality of sensors 2 capable of movementrelative to the scale 1 either in the positive direction, indicated by asolid arrow, or in the negative direction, indicated by a chain-linearrow. As a result of moving across the graduations of the scale l thesensors 2 transmit phase-shifted repetitive signals which are converted,in a known manner, into square-wave signals alternating between twologic levels and l, by comparison with a reference level, in a shaper 3.The signals so formed are fed to a code converter 4 which combines theshaped signals and supplies at its outputs 5 a plurality of networksignals of which each in turn, during a movement of the scanning,

device equal to the scale pitch p, includes a squarewave pulse of whichthe width corresponds to a movement unit or increment equal to p/n, nbeing the number of outputs 5 of the code converter 4.

The network signals are fed to a counting-pulse generating circuit 6which produces a short pulse upon the occurrence of a square-wave pulsein any of the network signals.

The pulses so generated are delayed in a time-delay circuit 7 and thenfed to a routing circuit 8 which, depending on the condition in which itis set, feeds the pulses either to the forward or adding input C of areversible counter 9, so that the pulses generated by the network 6 areadded as an absolute value to the total which is recorded by the counter9, and which represents the position reading for the scanning device onthe scale, or to the backward or subtracting input D of the counter 9,so that the pulses generated are subtracted as an absolute value fromthe total recorded by the counter.

The routing direction of the circuit 8 is controlled by a countingdirection determining system which comprises, first of all, a directionof movement discriminating network 111, which receives the networksignals provided at the outputs 5 from the code converter 4 and combinesthem to form movement direction pulses in the signals transmitted fromits two outputs, of which one corresponds to the direction of positivemovement, defined relative to the scale l and represented on the diagramby a solid arrow, and the other to the negative movement direction,represented by a chain-line arrow.

The signals from the two outputs of the movement directiondiscriminating network are stored in a movement direction storageflip-flop 12 which transmits two signals, of mutually opposite sign to acircuit 13 for generating a signal controlling the direction ofcounting, this signal being transmitted from the output of circuit l3and applied to operate the routing circuit 8. The circuit 13 alsoreceives the mutually opposite signals transmitted by a toggle 15 forstoring the sign of the position reading displayed by the add-subtractcounter 9. The toggle is preferably a D-type master-slave bistabletrigger circuit with an input 151 for manual presetting of the sign, twoinputs Q and 6 opposite to one another, an input D in response to asignal at which the signal from the output 6 is set, and an input T forcausing the toggle to change its state, the signal set at the input Dpassing to the output Q whenever a rising slope is fed to the input T.

The signal applied to the input T is transmitted by an AND gate 16 ofwhich the inputs receive respectively the routing direction controllingsignal from the output 14 of the circuit 13 and a signal transmitted bya test circuit 13 for detecting a change to zero in the position readingdisplayed by the counter 9.

Visual indicators connected to the outputs Q and 6 of the flip-flop 15can be arranged to display a positive or a negative arithmetic operatorin front of the position reading, as appropriate.

Whenever a pulse is transmitted from the output of the gate 16, acircuit 18 forms two supplementary pulses and these supplementary pulsesare added to the pulses formed by the generating circuit 6 and aretherefore counted like counting pulses.

in the system above described, the counting pulses are formedindependently of the determination of the counting direction. Thisprevents any spurious signals which may be formed in the countingdirectiondetermining network from being counted as counting pulses, andthe risk of such interfering pulses being recorded is greatly reduced.Also, the system just described provides a simple solution to theproblem of the position reading changing to zero. Assuming that theposition reading displayed is positive when movement takes placerelative to zero in the positive direction indicated by the solid arrow,and negative when movement takes place relative to zero in the negativedirection indicated by the chain-line arrow, the pulses produced by themovement of the scanning device must be subtracted if the initialreading is positive and movement is in the negative direction, untilzero is reached. When zero has been passed, however, the sign displayedmust change and also the pulses previously subtracted must be added, theabsolute value of the reading now increasing. Also, while movement wasin the negative direction, the digit due to appear after the zero shouldhave been a 9. When the readings become negative, the 9 should bereplaced by a ll, so that two supplementary pulses must be transmitted.

The system embodying the invention does this in a very simple fashion.

First of all, a sign corresponding to the sign selected for the readingsto right or to left of the zero is preset manually by means of thecontrol 151.

The discriminating network 11 transmits a pulse, for every movement ofone increment, at one or other of its outputs Ill, 112, correspondingrespectively to positive and to negative movement.

If the initial reading is positive and movement is in the positivedirection, the signals developed at the outputs of the flip-flop 12 donot change, and for every work 6, which have been delayed by the circuit7 so that routing can be effected, are thus caused to operate counter 9in the counting direction.

If movement is in the negative direction, on the other hand, the output112 transmits a pulse, which changes over the toggle 12 and inverts thesignals developed at the outputs of this toggle so that the signal fromthe output 14 of the circuit 13 reverses the routing circuit 8, thedelayed counting pulses then being caused to operate the counter 9 inthe negative direction. If movement continues in the negative direction,the signal from the output 14 remains the same until zero is reached.

The circuit 17 has recorded the successive changes to zero of thedecades stages of the counter 9. When the last decade changes to zero,the signal from the circuit 17 is inverted and the gate 16 transmits apulse which is fed to the input T of the toggle 15, so that the signalsprovided at the outputs Q and O are inverted. If movement stillcontinues in the negative direction, the signals from the toggle 12remain the same so that, at

the time the toggle 15 changes its state, the circuit 13 transmits fromits output 14 a signal which moves the routing circuit 8 into thecounting condition. At the same time the signal from the output of thegate 16 is converted by the circuit 18 into two phase-shifted countingpulses which are added to the pulses generated by the circuit 6, sothat, as already described, the digit displayed by the counter, which ina decimal system will have become a 9, changes to 1.

FIGS. 2 and 3 illustrate a particular embodiment of the networks andcircuits used in a system according to the invention.

The scale 1, provided with graduations having a pitch p, may be of anytype, for example optical or magnetic. The scanning device 2 comprises,for example, five cells a, b, c, d, e which, in the case of-an opticalscale, may receive the light transmitted through the scale 1, each cellbeing situated behind an individual slot in a screen (not shown).Obviously, any reading system may be used, for example a system usingmoir effects.

As the cells a to 2 pass across the graduations of the scale 1, thesignals which they develop pass first to conventional impedance matchers21 of which only one is shown in detail, and which supply signals ofidentical amplitude.

It is essential to the operation of the invention for the signals to beproperly in phase. For this reason it is particularly advantageous toshape the signals by comparing them with one another. The shaper 3therefore comprises five comparators 31, 32, 33, 34 and 35 in which eachsignal developed by a cell is compared with a signal developed byanother of the cells. In the embodiment illustrated the signal a fromthe cell a is compared with the signal d' from the cell d in thecomparator 31 to give a shaped signal A corresponding to a d. Similarly,shaped square-wave signals B to E are shaped from the signals developedby the cells a to e.

The system shown in FIG. 2 will use a NAND logic element formed,therefore, by NAND gates supplying a 0 logic signal when they receive 1logic signals at their two inputs and supplying a l logical signal inall other circumstances.

The signals A to E and their inverses A to E shaped by inverters 33 arefed to a code conversion matrix 4 formed of a plurality of inverters andNAND gates and producing the combination of signals shown in thefollowing truth table:

Si O l 2 3 4 5 6 7 8 9 AD Each of the output gates P P P of the codeconversion network provides a network signal, which is normally at level1 and which falls to level 0 during movement of the scanning devicethrough an increment equal to one-tenth of the pitch.

It is easy to verify, for example, that the gate P whose inputs receivethe signals A and 6, is at the 0 level when the scanning device isbetween 0 and 1. A L in-l0 code is therefore provided, enabling tenincrements to be distinguished within one track pitch.

As a NAND logic is being used, each gate P to P is followed by aninverter l to 1 each inverter in turn producing a square-wave signal oflevel 1 of which the duration corresponds to a movement of oneincrement.

The pulse generating network is made up of nine conventionaldifferentiating circuits such as 61, each connected to the output of anindividual one of the in- 'verters 1 to I, and supplying a briefpositive pulse for every rising slope in the signal developed by theassociated gate.

These counting pulses are fed to a multi-input OR gate 62 with 10 inputsand are delayed in a time-delay circuit 7, of which the time constant isselected so that routing can be initiated before the pulse arrives.

The network signals C to C developed at the outputs of the inverters 1to 1 during successive ones of the submultiple increments of movementare fed to a movement direction discriminating circuit 11 shown indetail in FIG. 3. Each signal C" developed during one of the submultipleincrements of movement is fed directly to an input of two of the NANDgates 1 14, 1 l5 and is also delayed in a conventional time-delaycircuit such as 113. The signal C" so delayed is fed both to the secondinput of that gate 114 which receives the undelayed signal C developedduring the preceding one of the submultiple increments of movement andto the second input of that gate 115 which receives the undelayed signalC developed during the succeeding one of the submultiple increments ofmovement; K is taken as increasing from 0 to 9 in the positive directionof movement of the scanning device. The gates 114 are connected to theinputs of a multiple-input NOR gate 116 followed by an inverter 118, andthe gates 115 are connected to the inputs of a multiple-input NOR gate117 followed by an inverter 119. It will be appreciated that theinverters 118, 119 normally transmit signals of level 0 when thescanning device is between the two boundaries of an increment; whenmovement is in the positive direction, one of the gates 1 15 records theconjunction of the signals C and C at the instant the boundary betweentwo consecutive increments is traversed and at this instant transmits a0 pulse of which the width is regulated by the time constant of theassociated timeedelay circuit 113. The gate 117 therefore develops a lpulse which is converted by the inverter 1139 into a pulse of equalwidth. Similarly, when movement is in the negative direction, the gate118 transmits a 0 pulse of which the width is determined by the timeconstant of the time-delay circuit 113, whenever the boundary betweentwo successive increments is passed.

The signals from the outputs of the inverters 118, 119 are fedrespectively to the RESET (l?) and SET (S) inputs of a bistable triggeror toggle composed of two NAND gates 120, 112i, whose outputs yieldmutually opposed signals 0 and 6, and operating as shown in thefollowing truth table:

RESET ET 1 1 OM OM Previous state As this table shows, the toggleremains in its previous state when the SET and RESET inputs receive 1signals, that is to say, when the scanning device is between the twoboundaries of an increment. lf, however, the RESET input receives a 0signal, that is, if the boundary between two increments is passed duringmovement in the negative direction, the output Q yields a 0 signal andthe output 6 a 1 signal.

The toggle for memorizing the sign of the position reading is a d-typemaster-slave bistable trigger (or flipflop) shown diagrammatically inFIG. 2 and having two outputs Q and 6 producing mutually invertedsignals, and an input 151 at which the sign can be preset manually.After selection of the origin of the scale, corresponding to the zeroposition reading, by means of a conventional circuit for presetting thecounter 9, therefore, the operator can be displayed if the scanningdevice is in a position to the right of the origin. It is necessary onlyto move the selector 152 to the position and to press the button 153 toproduce a 0" pulse at the SET input and thus to change the output Q to1, the toggle 15 operating as shown in the truth table just given fortoggle 12. For positive positions, that is, the output Q 9f the toggle15 transmits a l signal and the output Q a 0 signal.

The signal controlling the routing direction is transmitted by a NANDgate 130 receiving the signals transmitted by two NAND gates 131, 132.The gate 131 receives the signals from the output Q of the toggle 12 andfrom the output 6 of the toggle 15, and the gate 132 receives theopposite signals from the output Q of the toggle 15 and from the output6 of the toggle 12. When the initial reading is positive and movement isin the positive direction, therefore, the SET input of the togglereceives the "O" signals when the RESET input remains at l The outputs Qand 6 of the toggle 12, like the outputs Q and 6 of the toggle 15,respectively provide l and 0" signals, and the toggle 130, receiving lsignals at both its inputs, provides a 0 signal. Similarly, as will beappreciated, the gate 130 provides a l signal when the initial readingis positive and movement is in the negative direction. As a result, ifthe routing direction control signal is a 0,the reversible counter mustadd the pulses, whereas when the signal provided by the gate 130 is a l,the counter must subtract the pulses.

The routing circuit 8 therefore comprises two NAND gates 80, 81, each ofwhich receives at one input the pulses from the pulse generating networkand at the other input either (in the case of the gate 8%) a signaldirectly transmitted from the output of the gate 13% or (in the case ofthe gate 81) this signal inverted. When movement is in the positivedirection, therefore, the gate 81 always receives a 1 signal at oneinput, and it transmits a 0 signal whenever it receives a 1 countingpulse from the output of the time-delay circuit 7. The signal sotransmitted is re-inverted and fed to the counting input of the counter9. Conversely, when movement is in the negative direction, the gate always receives a 1 signal at one input and it transmits a 0 signalwhenever it receives a pulse from the output of the time-delay circuit7. it then transmits a 0 signal which is inverted and fed to thededucting input of the counter 9. Clearly, no interference spurioussignal occurring in the pulse direction discriminating network can beconfused with the counting pulses, because it is only during the briefinstant when a 1 counting pulse appears at an input of the gates 80 or81 that that one of these gates whose other input is at the 1 leveltransmits a signal which is effective upon the counter 9.

' When the initial reading is positive and movement is in the negativedirection, the decades of the counter 9 change successively to 0.

The test circuit 17 is formed of an inverter 171 connected to all theoutputs of the decades of the counter 9 by way of diodes which preventpulses passing from one counter to another, the common line beingearthed by way of a resistor. As long as any one or more of the decadesin the counter 9 is not at 0, therefore, the inverter 171 transmits a 0signal. When the scanning device passes through the position of theorigin, however, the first decade in the counter 9 changes to zero inits turn, and the output of the inverter 171 changes to l The signalsappearing at the outputs of the test circuit 17 and of circuit 13 arefed to a NAND gate 16. As long as the counter is not at 0, the input ofthe gate 16 connected to the test circuit receives a 0 signal and thegate 16 therefore transmits a 1 signal. When movement is in the negativedirection and the origin is crossed, both inputs of the gate 16 receivea l signal and the output signal changes to 0, exhibiting a descendingslope.

lf movement continues in the negative direction, the pulse generatingnetwork provides a pulse which tends to change the first decade in thecounter to 9. The signal transmitted by the gate 171 returns to O andthe signal at the output from the gate 16 returns to 1, exhibiting arising slope.

This rising slope is converted by a differentiating circuit 1S1 into apulse which is fed directly to the input of the gate 62 of the pulsegenerating network and is also converted by a monostable circuit 182into a second phase-shifted pulse also fed to the input of the gate 62,the phase-shift being regulated by the time constant of the monostablecircuit T82. The counter therefore receives two supplementary pulses, sothat it displays a 1 instead of the 9.

At the same time the signal of rising slope produced at the output ofthe gate 16 is fed to the T input-of the toggle 15 and causes the latterto change its state. The signal from the output 6, set by an inputsignal at the input D, now passes to the output Q, the output 6 thenchanging to l. The operator now displayed is therefore negative. Asmovement continues in the negative direction, the outputs Q, 6 of thetoggle 12 remain at the 0 and l levels respectively, and the gate 130transmits a 0 signal which, inverted into a l signal and fed to the gate81 reverses the routing, and the two delayed supplementary pulsesproduced by the circuits 181, 182 are therefore counted, with the resultthat the digit 9, which should have been displayed by the first decadeof the counter, changes to 1. Similarly, the following pulses arecounted if movement continues in the negative direction.

Clearly, if the initial reading is negative and movement is in thepositive direction, the pulses are at first subtracted. Then, when thescanning device passes the origin, the sign of the reading is changed atthe same time as the routing 8 is reversed, the pulses being countedagain.

By means of the system just described, which uses a small number ofsimple circuits, therefore, it is easy to select the origin of ameasurement and the sign of the readings displayed, the counting of thepulses by the counter-being merely delayed, at the time the origin isreached, by a negligible time long enough to reverse the countingdirection and the sign of the reading displayed.

Also, since the counter can only take into account counting pulsesshaped in a simple circuit connected in parallel with the circuitdetermination of the counting direction, the risk of interference beingrecorded is greatly reduced.

Obviously, the invention is not restricted to the details of theembodiments just described, and in particular equivalent systems mightbe substituted for the circuits and toggles described by way of example.Although all the systems described use a NAND logic, any other logiccould, of course, be used.

Similarly, the scanning device has been described diagrammatically byway of example, but might be replaced by any other device providing onepulse for each one increment of movement. The signal shaper and the codeconversion network may, of course, be replaced by any equivalent system.However, since the signals used must be perfectly in phase, it isparticularly advantageous to use the shaper described, in which eachsignal is compared with a signal developed by another detector. Thesignal transmitted by each detector can be compared with a combinationof signals transmitted by two of the other detectors so that the scalepitch, of course, can be subdivided into a larger number of increments,whereupon the counting system just described can easily be used merelyby increasing the number of inputs in the pulse generating network andin the movement direction discriminating network.

I claim 1. Apparatus for measuring or indicating movement by encodingand counting, comprising a graduated scale, a travel measuring devicehaving n output gates each providing a unique signal, these uniquesignals exhibiting in succession during movement equal to one scalepitch a square-wave pulse of which the width corresponds to oneincrement of movement, a first circuit means for generating one countingpulse for each increment of movement, a second circuit means fordetermining the direction of counting, and a reversible counter havingone input for pulses to be added and another input for pulses to besubtracted and supplying an algebraic value representing the positionrelative to an origin, of the travel measuring device, said first andsecond circuit means being connected in parallel between the n outputgates of the travel measuring device and a routing circuit which has twooutputs connected respectively to the adding and to the subtractinginputs of the reversible counter and which receives on one input thecounting pulses produced by the first circuit means and on another inputa signal, produced by said second circuit means, controlling the routingof the counting pulses to one input or the other of the counter whereinsaid second circuit means comprises a network for discriminating thedirection of movement, a toggle for storing the direction of movement, amanually preset master-slave toggle for storing the sign of the positionreading, a circuit operated by the output signals of the toggles forgenerating a signal controlling the direction of counting, a testcircuit for detecting a change to zero of the counter state, the outputof the circuit for controlling the direction of counting and that of thetest circuit being connected to the inputs of a gate of which the outputsignal is applied both to cause the sign-storing toggle to change itsstate and to the input of a circuit capable of forming two phaseshiftedsupplementary pulses which are arranged to be applied to the input forthe counting pulses of said routing circuit. 7

2. Measuring or indicating apparatus in accordance with claim 1, whereinsaid first circuit means comprises n respective differentiating circuitsfor the signals developed at the outputs of the movement measuringdevice, each of said differentiating circuits being connected betweenone of the said outputs and a respective input of a multiple-input ORgate of which the output is connected by way of a time-delay circuit tothe counting-pulse input of the routing circuit.

3. Measuring or indicating apparatus in accordance with claim 2, whereineach said differentiating circuit is arranged to develop a briefcounting pulse whenever the signal transmitted by the correspondingoutput of the travel measuring device includes a rising slope.

4. Measuring or indicating apparatus in accordance with claim 2, whereinthe output of the circuit for forming said two supplementary pulses isconnected to the input of said multi-input OR gate in said first circuitmeans.

5. Measuring or indicating apparatus in accordance with claim 1, whereineach of the n unique signals comprises a distinctive signal portiondeveloped during a unique l/n submultiple portion K of the scale pitch,where K increases from 1 to n during positive movement, and said secondcircuit means includes an individual delay circuit for equally delayingeach of said unique signals, n AND gates each fed with an undelayed oneof said unique signals and with the delayed unique signal developedduring a preceding submultiple increment of movement theoutputs of allsaid n AND gates being connected to respective inputs of amultiple-input OR gate yielding at its output a signal denotive ofmovement in one direction, and n further AND gates each fed with anundelayed one of said unique signals and with the delayed unique signaldeveloped during the succeeding increment of movement, the outputs ofall said further AND gates being connected to respective inputs of afurther multi-input OR gate yielding at its output a signal denotive ofmovement in the other direction.

6. Measuring or indicating apparatus in accordance with claim 5, whereinsaid toggle for storing the direction of movement comprises two NANDgates, each receiving both the signal from the output of the other ofsaid NAND gatesand also, in the case of said gate said signal denotiveof positive movement signal and, in the case of the other gate, saidsignal denotive of negative movement, the signals provided at theoutputs of the gates being mutually inverted.

7. Measuring or indicating apparatus in accordance with claim 5, whereinthe circuit for generating the signal controlling the direction ofcounting comprises two NAND gates, one receiving the signal denotive ofpositive movement from the toggle storing the direction of movement andthe positive signal from the sign-storing toggle and the other receivingfrom each of said toggles signals denotive respectively of negativemovement and of negative sign, the outputs of the two NAND gates beingconnected to the input of a further NAND gate of which the output isconnected to the input of the routing circuit.

8. Measuring or indicating apparatus in accordance with claim 1, whereinthe toggle storing the sign of the position reading is a mastenslavebistable circuit with two inputs for manual presetting of a sign, apositive output and a negative output, a setting input connected to thenegative output and an input for a signal causing the toggle to changeits state.

9. Measuring or indicating apparatus in accordance with claim 1, whereinthe circuit for forming said two pulses comprises a first time-delaycircuit arranged to delay the signals which are applied to cause achange of state of the sign-storing toggle, the output of said delaycircuit being connected directly to an individual input of themultiple-input OR gate of said first circuit means, and also, by .way ofthe series combination of an inverter, a monostable flipflop and asecond time-delay circuit, to another individual input of saidmultipleinput OR gate.

1. Apparatus for measurIng or indicating movement by encoding andcounting, comprising a graduated scale, a travel measuring device havingn output gates each providing a unique signal, these unique signalsexhibiting in succession during movement equal to one scale pitch asquare-wave pulse of which the width corresponds to one increment ofmovement, a first circuit means for generating one counting pulse foreach increment of movement, a second circuit means for determining thedirection of counting, and a reversible counter having one input forpulses to be added and another input for pulses to be subtracted andsupplying an algebraic value representing the position relative to anorigin, of the travel measuring device, said first and second circuitmeans being connected in parallel between the n output gates of thetravel measuring device and a routing circuit which has two outputsconnected respectively to the adding and to the subtracting inputs ofthe reversible counter and which receives on one input the countingpulses produced by the first circuit means and on another input asignal, produced by said second circuit means, controlling the routingof the counting pulses to one input or the other of the counter whereinsaid second circuit means comprises a network for discriminating thedirection of movement, a toggle for storing the direction of movement, amanually preset master-slave toggle for storing the sign of the positionreading, a circuit operated by the output signals of the toggles forgenerating a signal controlling the direction of counting, a testcircuit for detecting a change to zero of the counter state, the outputof the circuit for controlling the direction of counting and that of thetest circuit being connected to the inputs of a gate of which the outputsignal is applied both to cause the sign-storing toggle to change itsstate and to the input of a circuit capable of forming two phaseshiftedsupplementary pulses which are arranged to be applied to the input forthe counting pulses of said routing circuit.
 2. Measuring or indicatingapparatus in accordance with claim 1, wherein said first circuit meanscomprises n respective differentiating circuits for the signalsdeveloped at the outputs of the movement measuring device, each of saiddifferentiating circuits being connected between one of the said outputsand a respective input of a multiple-input OR gate of which the outputis connected by way of a time-delay circuit to the counting-pulse inputof the routing circuit.
 3. Measuring or indicating apparatus inaccordance with claim 2, wherein each said differentiating circuit isarranged to develop a brief counting pulse whenever the signaltransmitted by the corresponding output of the travel measuring deviceincludes a rising slope.
 4. Measuring or indicating apparatus inaccordance with claim 2, wherein the output of the circuit for formingsaid two supplementary pulses is connected to the input of saidmulti-input OR gate in said first circuit means.
 5. Measuring orindicating apparatus in accordance with claim 1, wherein each of the nunique signals comprises a distinctive signal portion developed during aunique 1/n submultiple portion K of the scale pitch, where K increasesfrom 1 to n during positive movement, and said second circuit meansincludes an individual delay circuit for equally delaying each of saidunique signals, n AND gates each fed with an undelayed one of saidunique signals and with the delayed unique signal developed during apreceding submultiple increment of movement the outputs of all said nAND gates being connected to respective inputs of a multiple-input ORgate yielding at its output a signal denotive of movement in onedirection, and n further AND gates each fed with an undelayed one ofsaid unique signals and with the delayed unique signal developed duringthe succeeding increment of movement, the outputs of all said furtherAND gates being connecteD to respective inputs of a further multi-inputOR gate yielding at its output a signal denotive of movement in theother direction.
 6. Measuring or indicating apparatus in accordance withclaim 5, wherein said toggle for storing the direction of movementcomprises two NAND gates, each receiving both the signal from the outputof the other of said NAND gates and also, in the case of said gate saidsignal denotive of positive movement signal and, in the case of theother gate, said signal denotive of negative movement, the signalsprovided at the outputs of the gates being mutually inverted. 7.Measuring or indicating apparatus in accordance with claim 5, whereinthe circuit for generating the signal controlling the direction ofcounting comprises two NAND gates, one receiving the signal denotive ofpositive movement from the toggle storing the direction of movement andthe positive signal from the sign-storing toggle and the other receivingfrom each of said toggles signals denotive respectively of negativemovement and of negative sign, the outputs of the two NAND gates beingconnected to the input of a further NAND gate of which the output isconnected to the input of the routing circuit.
 8. Measuring orindicating apparatus in accordance with claim 1, wherein the togglestoring the sign of the position reading is a master-slave bistablecircuit with two inputs for manual presetting of a sign, a positiveoutput and a negative output, a setting input connected to the negativeoutput and an input for a signal causing the toggle to change its state.9. Measuring or indicating apparatus in accordance with claim 1, whereinthe circuit for forming said two pulses comprises a first time-delaycircuit arranged to delay the signals which are applied to cause achange of state of the sign-storing toggle, the output of said delaycircuit being connected directly to an individual input of themultiple-input OR gate of said first circuit means, and also, by way ofthe series combination of an inverter, a monostable flipflop and asecond time-delay circuit, to another individual input of saidmultiple-input OR gate.